This Phase II SBIR project proposes to develop an electrical stimulation augmented exercise device for individuals with incomplete spinal cord injury (iSCI). The device will provide a closed-chain, load bearing lower extremity exercise that has the potential to condition muscles and reverse or slow the rate of loss of bone mineral density. Users will be encouraged to voluntarily perform the exercise. Client volitional efforts will be augmented by electrical stimulation and a servomotor drive such that the prescribed exercise range of motion is fulfilled with each movement cycle. The adaptive stimulation controller will continuously adjust the stimulation profile based on movement errors and servomotor activity to provide only the stimulation that is necessary to complete the exercise while encouraging clients to contribute their best volitional effort on each exercise cycle. A visual feedback infrastructure will be developed that encourages client participation, emphasizes clinically relevant therapeutic exercise goals, and rewards client achievements. The visual environment will require clients to generate a series of appropriately timed and executed volitional trigger events (ranging from 'trace levels of applied force'to 'unassisted movements') which will be rewarded with a full range of motion movement cycle and success in a game. We hypothesize that long-term use of the device in a comprehensive motor rehabilitation program may lead to functional improvements in addition to the localized and systemic benefits of exercise. Phase I feasibility milestones were achieved, including demonstration that: 1) client volitional effort could be synchronized with the stimulation controller;2) functional stimulation levels could be well tolerated in this population where cutaneous sensation is in-tact (potentially hypersensitive);and 3) the stimulation controller could accommodate client volitional effort and generate only the stimulation that was needed to elicit the desired exercise movement. We propose to build upon Phase I results through the following Phase II aims: 1) develop a servomotor drive that will improve exercise quality, provide a wider range and better control of bodyweight loading, allow use by individuals with advanced osteoporosis who are most in need of the exercise, and accomplish the goal of coordinating volitional and stimulation-augmented efforts via haptic feedback rather than a real-time visual display;2) develop intellectually engaging visual display environments that encourage and reward clinically relevant client volitional efforts;and 3) improve reliability and manufacturability. We will demonstrate efficacy via a two-site clinical trial in which twenty (20) individuals with chronic incomplete spinal cord injury participate in a 12-week exercise paradigm using the device. Outcome measures will include assessment of functional improvements (i.e., FIM, gait analysis) and a dynamometer test to assess improvements in volitional control independent of exercise-related improvements in torque generating capability. The target market for the device is clinics who serve individuals with neuromotor disabilities such as incomplete SCI, traumatic brain injury, or stroke. The device will be competitively priced within the electrical stimulation-based exercise equipment market. PUBLIC HEALTH RELEVENCE: The proposed work may benefit public health through development of a clinically viable, electrical stimulation based therapeutic exercise device for use in motor rehabilitation following spinal cord injury or stroke. Compared to existing devices and techniques, the adaptively controlled electrical stimulation, servomotor assist, and video game components and tight integration of instrumentation, control, stimulation, visualization, and reporting features may improve efficacy and availability of the therapeutic intervention for many affected individuals.